8482번 - Express Delivery 다국어

Your company, Byteland Express, has to deliver some parcels to clients located somewhere in the city. The city consists of 2×10⁹ + 1south-north streets and 2×10⁹ + 1 west-east streets (both numbered from 0 to 2×10⁹). A postman drives from one junction to a neighbouring one in one minute. The company is located next to the junction of streets number x_c and y_c.

All parcels have to be delivered as fast as possible, so driving to a client located next to the junction of the x-th and y-th street, can take at most (=exactly) |x_c - x| + |y_c - y| minutes. It takes a very short time to give a parcel to a client, so while driving to one client, a postman can give a parcel to another client (but cannot choose a longer route to do that). Your task is to determine how many postmen are needed to perform the delivery.

First line of input contains one integer N (1 ≤ N ≤ 1 000 000). Second line contains the location of the company, the following N lines contain locations of the clients. A description of a location consists of two integers: coordinates x and y (0 ≤ x, y ≤ 2×10⁹). Every two points (from among company or clients) differ on both coordinates (every x is different and every y is different).

In the only line of the standard output write one integer: the number of postmen needed to deliver parcels to all clients.